Multilayer video images include a plurality of layers, such as a background, a wallpaper and an opaque foreground, and a video layer in front of the background. Generally the video layer hides a portion of the background.
Typically the values of the pixels of all the layers of the image to be composed are stored in a memory. For composing the image, the values of the pixels of the image layers are read, then the image is composed from at least some of the values of the corresponding pixels in the various image layers.
However, the pixel values of the portion of the background hidden by the video layer are unimportant in composing the image, in that the pixels of this portion of the background are hidden by the video layer. The separate reading of the values of the pixels of all the layers of the image to be composed leads to a bandwidth in reading (i.e., the flow rate of data transferred from memory) which may be relatively high in some cases, whereas some background pixels will not be seen.